1. Field of Invention
The present invention relates to Voice Over IP (VoIP) systems, and in particular, to such systems that enable emergency calls in the event of loss of VoIP service.
2. Related Art
Voice over Internet Protocol (VoIP) telephone services are becoming more and more prevalent in today's communications. VoIP allows voice calls using Internet Protocol (“IP”) networks, such as the Internet, corporate intranets, or any IP network, as an alternative to traditional public switched telephone networks (“PSTN”). Unlike the PSTN, which is circuit-switched, the Internet is packet-switched. As such, communications on the Internet is accomplished by transmitting and receiving packets of data. In addition to data, each packet contains a destination address to ensure that it is routed correctly. The format of these packets is defined by the IP. One type of allowable data is encoded, digitized voice, known as Voice over IP. VoIP is voice that is packetized as defined by IP, and communicated over the Internet for telephone-like communication. Individual VoIP packets may travel over different network paths to reach the final destination where the packets are reassembled in correct sequence to reconstruct the voice information.
VoIP provides several advantages over PSTNs or POTS (Plain Old Telephone Service). First, there is a savings in money compared to the need to use traditional tolled telecommunications networks. Additionally, Voice over IP enables the management of voice and data over a single network. Further, with the use of IP phones, the costs and complexity for modifying the system are greatly reduced, such as when a user moves or needs to add or make changes. Moreover, additional and integrated new services, such as integrated messaging, bandwidth on demand, voice e-mails, the development of “voice portals” on the Web, simplified setting up and tearing down, and transferring of phone calls, are possible.
Using VoIP technology, phone systems can communicate with each other over existing IP data networks typically present between remote sites. This can eliminate the need for expensive, dedicated circuits between facilities. The shared bandwidth can also be used for voice calls and data communication simultaneously, so that no bandwidth is required to be dedicated to voice or data.
Another advantage of a VoIP system is the ability to implement a phone system over an existing data network that is already connecting workstations within a local area network, such as over an Ethernet. An Ethernet operates over twisted wire and over coaxial cable for connecting various devices, such as computers, printers, workstations, terminals, servers, and the like, within the same building or site. Because the Ethernet utilizes frame packets for transmitting information, VoIP can utilize such packet switching capabilities to connect IP phones onto the Ethernet.
While VoIP provides numerous advantages over the PSTN or POTS, such phone systems also present certain problems not associated with conventional telephone systems. For example, because communication is effected through the Internet, disruptions in the Internet can disrupt or degrade the VoIP communication, due to occurrences such as packet loss, packet delay, corrupted packets, and power outages. While such problems may be acceptable for purposes of data transmission and most voice communications, it is generally unacceptable for certain types of voice communications, such as emergency or 911 calls. In the event of a power outage or a loss in the broadband connection, the user will be unable to place a 911 call over the VoIP phone system. The user would then need to place the emergency call through another channel, such as a cell phone or a conventional land line phone. Even if such a channel were available, which may not always be the case, valuable time may be lost in placing the emergency call.
Therefore, there is a need for a VoIP phone system that is capable of connecting an emergency 911 call when a power failure occurs or when the broadband connection is down.
It should be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures.